As discussed in U.S. Pat. No. 4,498,681 issued Feb. 12, 1985 to Larry Heinz and incorporated herein by reference, a universal seal cage lantern ring, USCLR, is illustrated which provides for a flexible web, in which lands to one side of the web are formed in a continuous integral manner such that the lands to one side of the web form a continuous channel. The lands to the other side of the web are slotted to provide an intermittent land structure; and the web is provided with apertures through which fluid flows from the outer portion of the lantern ring to the inner channel where it may be dispersed about the shaft. Note, other U.S. Patents, namely U.S. Pat. Nos. 1,532,961; 501,207; 4,157,833; 1,514,192; and 1,653,439 illustrate various lantern ring configurations.
More particularly, with respect to U.S. Pat. No. 4,498,681 there has been some difficulty with snapping of lantern rings made with continuous lands when such a lantern ring is made from polytetrafluoroethylene, PTFE, and is formed to fit about a relatively small diameter shaft with the continuous land structure installed to the inside of the ring. The reason attributable to the breakage of the lantern ring is that the continuous land structure is relatively rigid and is not elastic enough to deform when wrapped around a small shaft. This results in the snapping of the lantern ring when forming the ring about a small radius. Even if the lantern ring does not break at this time it may fracture, such that when it is placed in a stuffing box and sequentially installed with packing rings, the installed lantern ring may break at the fracture point during the tightening of the gland.
Since there are large numbers of applications involving small diameter shafts, less than 11/2" in diameter, and since snapping of the lantern rings is extremely costly, especially where as many as 3,000 pumps in a single plant may be involved, the ability to provide a reusable ring from a roll which will survive rough handling offers considerable cost savings.
Moreover, when, as directed, such a lantern ring structure is wound about a shaft with the intermittent lands adjacent the shaft, removal of such a packing ring is difficult when utilizing a corkscrew type packing puller, as is common in the industry. This is because the corkscrew point usually digs into the continuous land when it is screwed into the lantern ring for the purpose of its removal. The reason that the point digs into the continuous land is because the corkscrew tends to run down the wall or the bore of the surrounding stuffing box, such that the point of the corkscrew meets up with the continuous land and screws into it. When the corkscrew pulls out the lantern ring during removal, the continuous land breaks as the lantern ring is pulled out.
Additionally, for large diameter shafts, normally in excess of 31/2 inches in diameter, the aforementioned lantern ring tends to rotate with the shaft if any contact is made with the shaft. This occurs unless there is clearance between shaft and lantern ring assured by measurement; or unless sufficient frictional Pressure is provided between the packing adjacent the lantern ring and the lantern ring itself. In the modern climate of haste to bring equipment back on line, both steps to prevent rotation are increasingly lacking. It will be appreciated that lantern ring rotation results in wear which promotes leakage. In the past, for large diameter shafts, the user was directed to use the Heinz ring with the continuous lands on the outside of the ring. This prevented packing rings on either side of the lantern ring from locking into the lantern ring, which would have prevented lantern ring rotation. Note also that for large diameter shafts, the shaft surface is within a few percent of the stuffing box bore surface, so that in normal usage, lantern rings tend to rotate with the large diameter shaft whenever shaft to lantern ring contact occurs.